I use Best Bowling (free) for the iphone. It tracks scores, leaves, spare %, carry %, and many other neat things. I know that there are others out there, but this one gives me more than enough features.

I use pinpal also there was a one time fee. its a great app for sure.

if you have a android, Frames works nice cost $10.00 but there is a trial version
http://www.warilysoftware.com/

This is the one that I use.  Love it.

I use Bowling ScoreKeeper on my Android.  Free and works perfectly for tracking scores and averages. 

https://play.google.com/store/apps/details?id=com.cmr.droid.scorekeeper&hl=en

I'm using Perfect Game for iPhone. It has a small one time fee. There are a lot of good features that you can use or you can just input your scores.

I saw this app before. Just like the palm pilot (I feel old) version, it has the board function. The PinPal doesn't have that. If the pair/lanes are playing differently, I have to write notes where I'm standing on the league sheet. I have short term memory lol. Plus, I bowl second shift, it's my bed time if I wasn't bowling.